JPS62275090A - Production of semi-insulating semiconductor single crystal - Google Patents

Abstract

PURPOSE:To obtain a high quality single crystal having increased specific resistance, maintaining uniformity and depositing fo secondary crystal by using a molten III-V compound semiconductor contg. Fe, Cr or Co and by specifying crystal orientation at the time of pulling. CONSTITUTION:A molten III-V compound semiconductor contg. one or more among Fe, Cr and Co is used as starting material. The semiconductor may be indium phosphide. Crystal orientation is set to <111> at the time of pulling and a semi-insulating semiconductor single crystal is pulled up by conventional LEC method. Thus, a single crystal having slightly lower specific resistance at the peripheral part but high specific resistance at the central part and a uniform distribution of specific resistance in a cross-section can be obtd., so wafers having high specific resistance can be easily obtd. by slightly cutting off the peripheral part of the crystal.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a method for manufacturing a semi-insulating II-V group compound semiconductor single crystal to be used as a substrate for a semiconductor device. be.

"Prior Art and Problems" As is well known, semi-insulating gallium arsenide and semi-insulating innoum phosphide are used as substrates for various microwave devices, optical devices, magnetic devices, and the like.

Recently, a technology for implanting ions into this substrate has been developed, and integrated HF circuit (IG)? The field of application to large-scale integrated circuits and i-circuits (LSI) has opened up. Since some kind of heat treatment is added during processing such as ion implantation, it is essential that the electrical characteristics of the substrate be thermally stable.

Furthermore, as a substrate for IC and LSI, the specific resistance is [0
Higher resistivity than conventional semi-insulating ones of around °Ω・cm, for example, 107 to 10′Ω・cm at 300°.
It is required that:

Conventionally, the following measures have been taken to satisfy the above conditions for gallium arsenide.

(a) Crystal growth method that involves doping with chromium.

(b) Crystal growth method by doping oxygen.

(c) Undoped crystal growth method with low impurity concentration.

Of these, (a) and (b) are electrically conductive by doping Si, Cu, Ga, and As vacancies, which become conductive impurities in the crystal, and a complex of these vacancies and impurities. This is a method of compensating for

In method (a), doping control is difficult because the width coefficient of chromium relative to gallium arsenide is small, about 6 x 10-', and it is extremely difficult to enter the crystal.

In addition, if excessive chromium is doped to stabilize electrical characteristics, many defects and precipitates will occur due to dislocation density, while if a small amount of chromium is doped, it will tend to become thermally unstable. There is a point.

The method (b) has the drawbacks that doping control is difficult and thermal stability is poor.

In addition, in the method (c) above, as a method for effectively realizing it, there is a direct synthetic liquid capsule pulling method or Pekarek et al; Czech, J, Ph.
ys, 20(+970)]. Conventional liquid capsule pulling method (LEC method, Liquid
Encapsulated Cz.

Chraski method) uses gallium arsenide that has been synthesized once as a raw material and therefore incorporates a large amount of impurities, whereas this method directly synthesizes gallium and arsenic under high pressure and performs pulling growth, so it is difficult to incorporate impurities. It is said that this makes it a so-called "intrinsic semiconductor". However, at present, even crystals grown using this method have a high concentration of impurities, and due to the need for high pressure, the internal structure of the furnace is different from conventional ones, making pulling growth difficult. Furthermore, like the conventional pulling method, there are many problems such as deviation from stoichiometry and high dislocation density.

In addition, in the case of indium phosphide, undoped crystals are not semi-insulating, so either they are doped with Fe, Cr, Co, etc. to obtain semi-insulating crystals, or they suffer from the same problems as mentioned above and cannot be used as semiconductors of a certain quality. It has become difficult to produce devices with a high yield.

The present invention has been made in view of the above circumstances, and its purpose is to increase the specific resistance in the single crystal while maintaining its uniformity when producing a semi-insulating single crystal, and to The object of the present invention is to provide a method for obtaining a high-quality single crystal without crystallizing a secondary phase.

"Means for Solving the Problems" The method for manufacturing a semi-insulating semiconductor single crystal according to the present invention includes Fe
5Cr, Co added one kind of element [-V
Using a group compound semiconductor melt, the crystal orientation is <l I l
＞It is characterized by being able to pull up.

``Operation'' The method of the present invention having the above configuration has a facet (fac
eL) This method takes advantage of the fact that growth occurs and the effective segregation coefficient of impurities increases in that region.

When crystals are crystallized from a melt containing impurities, the impurity concentration in the melt changes as solidification progresses, and the impurity concentration in the crystal solidified from the melt changes accordingly. To go. If the impurity concentration in the residual melt exceeds the solid solubility limit, the secondary phase will be eliminated. Therefore, even if an attempt is made to dope a large amount of impurity (Fe) to increase the resistivity, the amount of impurity (Fe) may not be doped or defects may easily appear, resulting in poor crystal yield.

Therefore, if the effective segregation coefficient is high, when crystallization occurs from the same impurity concentration in the melt, the amount of impurities doped into the crystal will increase, and conversely, the amount of impurities remaining in the melt will increase. can be kept low. As a result, there is a margin up to the solid solubility limit, the yield of crystals with a high tope concentration increases, and the generation of secondary phases is observed.

In the present invention, although there may be a portion of slightly low resistivity at the periphery of the growing crystal, at the center of the crystal the resistivity is much higher than that of conventional crystals, and moreover, even in the same cross section It is possible to obtain a single crystal with extremely uniform distribution of . Therefore, by cutting the peripheral portion of the crystal to some extent, it is possible to easily obtain a wafer with high resistance.

To select the pulling direction, use a seed crystal whose growth surface is aligned with <l I 1>. Also, the pulling conditions for indium phosphide single crystal are as follows: Using high-purity indium phosphide with a concentration of 5 x 10" cm-3 or less,
The e-concentration may be determined appropriately from 0.01 to 0.07 wL%, and other values may be determined according to the usual LEC method. Further, in the present invention, it is possible to utilize a magnetic field with a magnetic field strength of 800 degrees or more.

Next, the present invention will be explained in detail.

"Example" A single crystal of indium phosphide having a diameter of 2 inches was pulled under the following conditions.

- Raw material: Indium phosphide with a carrier concentration of 10 x 1015 cm"3 and an Fe addition amount of O.025 wt% in the initial melt.

- Pulling method: The normal LEC method was followed except that the lifting direction was set to <III>.

The wafer was cut out from 172 positions in the length direction of the single crystal after being pulled, and the internal surface distribution of resistivity was measured (a total of 120 points were measured, selected from multiple directions in the radial direction from the center). The measurement results are shown in Figure 1.

As is clear from FIG. 1, in the crystal obtained according to the present invention, although a decrease in resistivity is observed at the outer periphery of the crystal, most of the central region has a high resistivity of IO8Ω・cm or more, and The standard deviation of was 7%.

"Effects of the Invention" As explained above, according to the method of manufacturing a semi-insulating semiconductor single crystal according to the present invention, although a portion with a slightly low resistivity occurs at the periphery of the grown crystal, at the center of the crystal,
It is possible to obtain a single crystal that has a much higher resistivity than conventional crystals and has an extremely uniform distribution of resistivity in the same cross section.

Therefore, with the crystal obtained by the method of the present invention, it is possible to easily obtain a wafer with high resistivity by cutting the periphery to some extent.

[Brief explanation of drawings]

FIG. 1 is a graph showing the specific resistance distribution within a cut plane at a position half in the length direction of an indium phosphide single crystal obtained by the method of the present invention.

Claims (1)

[Claims] When manufacturing compound semiconductor single crystals by the LEC method,
I added with one element selected from Fe, Cr, and Co
1. A method for producing a semi-insulating semiconductor single crystal, using a II-V group compound semiconductor melt and setting the crystal pulling direction to <111>.